Such closure or fastening elements for inserting into a bore, for example, in an engine, with a sleeve-shaped base body that can be inserted into the bore and with a splaying body that can be braced in the bore are known. Closure elements of this type are inserted, in particular as mass-produced items, into bores with different diameters and internal pressures for the purpose of sealing. Depending on the size of the bore and the strength of the effective internal pressure very different embodiments are produced, as disclosed for example in U.S. Pat. No. 6,708,978 B2. The closures described here are in the form of one-part closure discs. They are therefore easier to produce technically than multi-part closures, as described for example in publication WO 2009/000317 A1.